Mold for making castings of aluminum and aluminum alloys.



UNITED STATES PATENT OFFICE.

EARL BLOUGH, 0F rARNAssus' PENNSYLVANIA, AssIcNoR T0 ALUMINUM COMPANY orAMERICA, or PITTSBURG, PENNSYLVANIA, A CORPORATION or PENNSYLVANIA.

' Specification of Letters Patent.

' Pat nte M rch 23, 11909.

App ication filed November 11, 907. Serial .No. 401,787.

To all whom it may concern:

Be it known that I, EARL BLOUGH, a citizen ofthe United States, andresident of Parnassus, Westmoreland county, and State of Pennsylvania,have made new and useful Inventions Relating to Molds for MakingCastings of Aluminum and Aluminum Alloys, of which the following is aspecification.

This invention relates to molds for casting aluminum and aluminumalloys, and relates especially 1 to molds comprising ordinaryfoundrysand and carbonaceous diificultly oxidizable material of a densecharacter, the aluminum alloys being quickly chilled and thus givenincreased strength and toughnessby reason of theincreased heatconductivity of the mold caused by the carbonaceous material. For thispurpose 10 to 20 per cent. or so of finely ground carbonaceous materialmay be incorporated with ordina foundry sand without impairing itsdesiral le qualities in green sand molding, although, of course, theproportion of car onaceous material .used

a may vary considerably. 25

The carbonaceous material is preferably dense, difficultly oxidizableand comprises crystalline carbonaceous material so ,as to best give thedesired increase of heat conductivity'to the mold and efiect the roperchilling of the casting. Suitable fixed dlflicultly oxidizablecarbonaceous material may be prepared by finely grinding 50 arts of oodpetroleum coke and 25 parts 0 electric ight carbon or similar materialand thor oughly incorporating them with 25 parts of coal tar pitch as ina suitable kneading machine. The mixture may be formed into suitablebloclis under heavy pressure in any desired apparatus, such as anextrusion press, and the molded ieces are then preferably thoroughly caronized for a considerable time at hightem erature. This may be readilydone by pac ing them in a suitable electric furnace and subjecting themfor ten days or more to an intense heat greatly in excessof the heat ofthe metal used In this way the volatile material is thoroughly expelledand the carbon is given a very dense apparently crystalline'structure soas to be a verv good heat conductor and diflicultly oxidizable.

This material may be groundin any way to the desired fineness whichshould approximate that of the sand with which it is incorporated. Forordinary fine castings where a good grade of foundry sand is used thiscarbonaceous material may be ground so that about 85% asses through ahundred mesh sieve and a out passes through a two hundred mesh sieve.

When 15% or so by volume of this fine fixed carbonaceous material isthoroughly incorporated with ordinar foundry sand the bondin propertiesof t e. sand are substantial y unimpaired and green sand molds may bemade with the same facility as where ordinary foundry sand alone isemployed.

-When such molds are poured in the casting of aluminum alloys the metalin contact with the face of the mold is suddenly chilled by reason ofthe increased conductivity of the mold caused by this highly conductivecarbonaceous material and the castings are given a finely crystallinestructure and a very considerable increase inv tensile strength. With anordinary aluminum alloy containing about 8% of copper the ,tensilestrength is increased from 15% to 25% in this manner. The castings havethe same soundness as castings formed in ordinary sand molds, since theventing qualities of the sand are unimpaired by the incorporation ofsuch carbonaceous material which also because of its fixed characterdoes not cause blowin when the hot metal comes into contact therewith.Molds made of this material can be dumped and the sand riddled Withoutdifficulty, and as the carbonaceous material 1 is notreadilyoxidizablethe sand may be used repeatedly without special treatment andWithout substantial diminution of its valuable chilling properties, onlyneedin to be sufiiciently dampened or tempered be ore being forced intothe flasks to-form molds in the ordinary green sand moldin process. Theingredients specified in the i1 ustrative composition may be replaced inwhole or in part by other carbonaceous material, preferably of a denseor crystalline character and having the other properties referred to.

Having described. this invention in con-. nection with illustrativemolds, compositions and methods of procedure, to the details of whichdisclosure the invention is not, of course, to'be limited, what isclaimed as new and What is desired to be secured by-Letters Patent isset forth in the appended claims. 1. The green sand mold for makingcastings of aluminum alloys formed from ordinary foundry sand with whichabout 15% of finely ground, dense, diificultly oxidizable, carbonaceousmaterial, substantially fixed at the heat of the molten metal used, hasbeen incorporated to chill the metal and strengthen the casting by 'theincreased heat conductivity of the mold.

2. The green sand mold for making castings of aluminum alloys formedfrom ordinary foundry sand with which a considerable proportion offinely ground, dense, carbonaceous material, substantially fixed at theheatof the molten metal used, has been incorporated Without destroyingthe bonding properties of the sand, to quickly chill the metal andstrengthen the casting by the increased heat conductivity of the mold.

3. The green sand mold for making castings comprising aluminum formedfrom ordinaryfoundry sand with which a considerable proportion ofcarbonaceous ma terial, substantially fixed at the heat of the moltenmetal, has been incorporated without destroying the bonding propertiesof the sand, to quicklychill the metal and strengthen the casting by theincreased heat conductivity of the mold.

4. The green sand mold for making castings comprising aluminum formedfrom sand with which a considerable pro ortion of carbonaceous materialhavin su stantially the same fineness as the san has been incorporated,to quickly chill the metal and strengthen the casting by the increasedheat conductivity of the mold.

5. The green sand mold for making castings comprisingconsiderableproportions of aluminum formed from sand with which aconsiderable proportion of ground, highly heat-conductive, inertmaterial substantially fixed at the heat of the molten metal used hasbeen incorporated to strengthen the casting by the increased chillingaction of the mold upon the metal used.

6'. The green sand mold for making castings comprising aluminum formedfrom ordinary foundry sand with which less than of ground, difiicultlyoxidizable, carbonaceous material, substantially fixed at the heat ofthe molten metal used, has been incorporated without destroying thebonding properties of the sand to strengthen the casting by'theincreased chilling action of the mold upon the metal used.

7. The green sand mold for making castings comprising aluminum formedfrom the material substantially free from carbonaceous material volatileat the heat of the metal used, and comprising less than 25% of ground,diificultly oxidizable, heat conductive material to strengthen thecasting by the increased chilling action of the mold on the metal used.

EARL BLOl GI-l. Witnesses:

E. D. CREE, J. L. MOLAMMON

